Stain resistant nylon carpets enjoy significant market acceptance. Stain resistance is typically imparted to nylon by treating the fiber as a solid filament or in a carpet form by the application of a chemical finish as described in the following U.S. patents to Monsanto: U.S. Pat. Nos. 4,501,591; 4,592,940; and 4,839,212.
Nylon carpet fiber is generally classified as to type, depending upon its receptivity to acid dyes and basic or cationic dyes. Cationic dyeable nylons contain SO.sub.3 H groups or COOH groups within the polymer structure in an amount sufficient to render the nylon fiber dyeable with a cationic dye which groups are receptive to cationic or basic dyes. Acid dyeably nylons are essentially conventional nylons, such as polyhexamethylene adipamide and polycaprolactam. Acid dyeable nylons vary as to type and are characterized as being weakly dyed with acid dyes, average dyed with acid dyes, or deeply dyed with acid dyes.
Cationic dyeable nylons generally exhibit inherent stain resistant properties, especially to acid-type stains, as compared to other nylon types used for carpet. Cationic dyeable nylons are dyeable with selected cationic dyes, but suffer from poorer lightfastness, especially in light shades, than do comparable shades dyed on acid dyeable nylon using monosulfonated or premetalized acid dyes. This has resulted in the under-utilization of cationic dyeable nylon as a carpet fiber. The fiber's inherently useful properties which otherwise make it attractive as a carpet fiber previously have not been fully realized.
This invention provides a procedure for dyeing cationic dyeable nylon with acid and premetalized acid dyes resulting in nylon carpet having improved stain resistance and fastness properties.
The preferred techniques for practicing the invention include exhaust dyeing, pad/steam dyeing, continuous carpet dyeing and the like. Illustrative examples for dyeing procedures thought to be suited to the process of this invention are: